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. Author manuscript; available in PMC: 2010 Aug 21.
Published in final edited form as: Lab Chip. 2009 Jun 10;9(16):2348–2355. doi: 10.1039/b902292a

Fig. 1. Oscillatory shear flow stretches DNA molecules.

Fig. 1

(A) Cartoon of DNA elongation by shear flows in a microchannel. Reverse flow maintains a DNA’s elongated conformation in a laminar flow and locks molecules within the same imaging plane (B) Parabolic shear flow profile in a square channel calculated and using MATLAB using equation (5) in the Experimental section19. (C) Fluid velocities (forward “+”; backward “−“), under oscillatory flow were estimated by time-lapse imaging of a fluorescent bead in a microchannel (60 μm × 40 μm × 8 mm driven by a 1.6 nL/sec in average, flow at 1.7 Hz (square wave; dashed lines). The use of 40× objective (vs. 63×, or 100× used for other experiments) enabled a wider view of a fluorescent bead near the side wall. Measured fluid velocity compared to the driving frequency (dashed line) shows hysteresis effects and distortion.